Backlog: O6 done e4cd0c540dab

- [x] O10b Parallel snapshot work: rendering the base state's files, building file graphs from a checkpoint, and reading working-copy files now run on every core (rayon).

- [ ] O10c Snapshot without the whole base (rest of O10): load only the file graphs a snapshot needs (a checkpoint split per file or indexed), skip reading and rendering files whose stat matches a manifest written for the same base, cache materialized states. Needs a spec change to the checkpoint format; target spec §25.

- [x] O5 Concurrency: two processes committing, snapshotting and pushing on one repository; locks hold, nothing is lost.

- [ ] O7 Shell completions (`oxy completions bash|zsh|fish`) and man pages generated from clap.

- [ ] O8 Git round trip on real history: import a scratch mirror of tetriblox (never the live repo), export it back, compare trees at every commit.

- [ ] O9 Portability review for macOS and Windows: path separators, executable bits, case-insensitive file systems, CRLF; tests where it can be exercised on Linux.

- 2026-09-28 H4 done: `/{owner}` profile (identicon, display name, bio, location, website, keys, organisations, visible repositories, activity by that person; never the email) and organisation page (description, members and roles, teams with sizes, repositories, activity); `/avatar/{name}` identicons also in the header and feeds; migration 0008 (bio, website, location) and Settings fields (http(s) websites only); `avatar` and `help` reserved. Test `profile_and_organisation_pages`; screenshot checked; deployed (andymccall profile 200 on Earth).

- 2026-09-28 O5 done. **Real bug fixed**: concurrent commands overwrote `.oxy/ops/head`, so the loser's operation (and its commit on the bookmark) vanished; a two-workspace test lost about half its commits every run. The head now moves by compare-and-swap under a short `.oxy/ops/lock`, and a mover that lost the race records a merge op (two parents, three-way merged view; bookmarks keep both sides' heads), as spec §12.1 described; undo refuses on a moved head. Tests: concurrent two-workspace commits with pushes lose nothing (5/5 runs), deterministic merge of two ops from one parent; two real oxy processes x 25 commits keep all 50 (39 merges). Spec §12.1 updated. Hub redeployed.

- 2026-09-28 H5 done: word-level marks within paired changed lines, `?w=1` hides whitespace-only changes (change, compare, proposal files), collapsible files (over 400 rows start closed), unified/split toggle remembered in a `diff` cookie, collapse/expand all. Tests: two renderer unit tests and `diffs_mark_words_hide_whitespace_and_collapse`; split view checked by screenshot; hub spec §6.8.1; deployed.